POSIX-compatible regex interface

With some ARE extensions

Signed-off-by: Steve Bennett <steveb@workware.net.au>

1 files changed, 1375 insertions, 0 deletions

diff --git a/jimregexp.c b/jimregexp.c
new file mode 100644
index 0000000..90c8dd7
--- /dev/null
+++ b/jimregexp.c
@@ -0,0 +1,1375 @@
+/*
+ * regcomp and regexec -- regsub and regerror are elsewhere
+ *
+ *	Copyright (c) 1986 by University of Toronto.
+ *	Written by Henry Spencer.  Not derived from licensed software.
+ *
+ *	Permission is granted to anyone to use this software for any
+ *	purpose on any computer system, and to redistribute it freely,
+ *	subject to the following restrictions:
+ *
+ *	1. The author is not responsible for the consequences of use of
+ *		this software, no matter how awful, even if they arise
+ *		from defects in it.
+ *
+ *	2. The origin of this software must not be misrepresented, either
+ *		by explicit claim or by omission.
+ *
+ *	3. Altered versions must be plainly marked as such, and must not
+ *		be misrepresented as being the original software.
+ *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
+ *** hoptoad!gnu, on 27 Dec 1986, to add \n as an alternative to |
+ *** to assist in implementing egrep.
+ *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
+ *** hoptoad!gnu, on 27 Dec 1986, to add \< and \> for word-matching
+ *** as in BSD grep and ex.
+ *** THIS IS AN ALTERED VERSION.  It was altered by John Gilmore,
+ *** hoptoad!gnu, on 28 Dec 1986, to optimize characters quoted with \.
+ *** THIS IS AN ALTERED VERSION.  It was altered by James A. Woods,
+ *** ames!jaw, on 19 June 1987, to quash a regcomp() redundancy.
+ *** THIS IS AN ALTERED VERSION.  It was altered by Christopher Seiwald
+ *** seiwald@vix.com, on 28 August 1993, for use in jam.  Regmagic.h
+ *** was moved into regexp.h, and the include of regexp.h now uses "'s
+ *** to avoid conflicting with the system regexp.h.  Const, bless its
+ *** soul, was removed so it can compile everywhere.  The declaration
+ *** of strchr() was in conflict on AIX, so it was removed (as it is
+ *** happily defined in string.h).
+ *** THIS IS AN ALTERED VERSION.  It was altered by Christopher Seiwald
+ *** seiwald@perforce.com, on 20 January 2000, to use function prototypes.
+ *** THIS IS AN ALTERED VERSION.  It was altered by Christopher Seiwald
+ *** seiwald@perforce.com, on 05 November 2002, to const string literals.
+ *** THIS IS AN ALTERED VERSION.  It was altered by Steve Bennett <steveb@workware.net.au>
+ *** on 16 October 2010, to remove static state and add better Tcl ARE compatibility.
+ *
+ * Beware that some of this code is subtly aware of the way operator
+ * precedence is structured in regular expressions.  Serious changes in
+ * regular-expression syntax might require a total rethink.
+ */
+#include <stdio.h>
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "jim.h"
+#include "jimregexp.h"
+
+#if !defined(HAVE_REGCOMP) || defined(JIM_REGEXP)
+
+/*
+ * Structure for regexp "program".  This is essentially a linear encoding
+ * of a nondeterministic finite-state machine (aka syntax charts or
+ * "railroad normal form" in parsing technology).  Each node is an opcode
+ * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
+ * all nodes except BRANCH implement concatenation; a "next" pointer with
+ * a BRANCH on both ends of it is connecting two alternatives.  (Here we
+ * have one of the subtle syntax dependencies:  an individual BRANCH (as
+ * opposed to a collection of them) is never concatenated with anything
+ * because of operator precedence.)  The operand of some types of node is
+ * a literal string; for others, it is a node leading into a sub-FSM.  In
+ * particular, the operand of a BRANCH node is the first node of the branch.
+ * (NB this is *not* a tree structure:  the tail of the branch connects
+ * to the thing following the set of BRANCHes.)  The opcodes are:
+ */
+
+/* This *MUST* be less than (255-20)/2=117 */
+#define REG_MAX_PAREN 100
+
+/* definition	number	opnd?	meaning */
+#define	END	0	/* no	End of program. */
+#define	BOL	1	/* no	Match "" at beginning of line. */
+#define	EOL	2	/* no	Match "" at end of line. */
+#define	ANY	3	/* no	Match any one character. */
+#define	ANYOF	4	/* str	Match any character in this string. */
+#define	ANYBUT	5	/* str	Match any character not in this string. */
+#define	BRANCH	6	/* node	Match this alternative, or the next... */
+#define	BACK	7	/* no	Match "", "next" ptr points backward. */
+#define	EXACTLY	8	/* str	Match this string. */
+#define	NOTHING	9	/* no	Match empty string. */
+#define	STAR	10	/* node	Match this (simple) thing 0 or more times. */
+#define	PLUS	11	/* node	Match this (simple) thing 1 or more times. */
+#define	WORDA	12	/* no	Match "" at wordchar, where prev is nonword */
+#define	WORDZ	13	/* no	Match "" at nonwordchar, where prev is word */
+#define	OPEN	20	/* no	Mark this point in input as start of #n. */
+			/*	OPEN+1 is number 1, etc. */
+#define	CLOSE	(OPEN+REG_MAX_PAREN)	/* no	Analogous to OPEN. */
+#define	CLOSE_END	(CLOSE+REG_MAX_PAREN)
+
+/*
+ * The first byte of the regexp internal "program" is actually this magic
+ * number; the start node begins in the second byte.
+ */
+#define	REG_MAGIC	0234
+
+/*
+ * Opcode notes:
+ *
+ * BRANCH	The set of branches constituting a single choice are hooked
+ *		together with their "next" pointers, since precedence prevents
+ *		anything being concatenated to any individual branch.  The
+ *		"next" pointer of the last BRANCH in a choice points to the
+ *		thing following the whole choice.  This is also where the
+ *		final "next" pointer of each individual branch points; each
+ *		branch starts with the operand node of a BRANCH node.
+ *
+ * BACK		Normal "next" pointers all implicitly point forward; BACK
+ *		exists to make loop structures possible.
+ *
+ * STAR,PLUS	'?', and complex '*' and '+', are implemented as circular
+ *		BRANCH structures using BACK.  Simple cases (one character
+ *		per match) are implemented with STAR and PLUS for speed
+ *		and to minimize recursive plunges.
+ *
+ * OPEN,CLOSE	...are numbered at compile time.
+ */
+
+/*
+ * A node is one char of opcode followed by two chars of "next" pointer.
+ * "Next" pointers are stored as two 8-bit pieces, high order first.  The
+ * value is a positive offset from the opcode of the node containing it.
+ * An operand, if any, simply follows the node.  (Note that much of the
+ * code generation knows about this implicit relationship.)
+ *
+ * Using two bytes for the "next" pointer is vast overkill for most things,
+ * but allows patterns to get big without disasters.
+ */
+#define	OP(p)	((unsigned char)*(p))
+#define	NEXT(p)	(((*((p)+1)&0377)<<8) + (*((p)+2)&0377))
+#define	OPERAND(p)	((p) + 3)
+
+/*
+ * See regmagic.h for one further detail of program structure.
+ */
+
+
+/*
+ * Utility definitions.
+ */
+#ifndef CHARBITS
+#define	UCHARAT(p)	((int)*(unsigned char *)(p))
+#else
+#define	UCHARAT(p)	((int)*(p)&CHARBITS)
+#endif
+
+#define	FAIL(R,M)	{ (R)->err = (M); return (M); }
+#define	ISMULT(c)	((c) == '*' || (c) == '+' || (c) == '?')
+
+/*
+ * Flags to be passed up and down.
+ */
+#define	HASWIDTH	01	/* Known never to match null string. */
+#define	SIMPLE		02	/* Simple enough to be STAR/PLUS operand. */
+#define	SPSTART		04	/* Starts with * or +. */
+#define	WORST		0	/* Worst case. */
+
+/*
+ * Forward declarations for regcomp()'s friends.
+ */
+static char *reg(regex_t *preg, int paren /* Parenthesized? */, int *flagp );
+static char *regpiece(regex_t *preg, int *flagp );
+static char *regbranch(regex_t *preg, int *flagp );
+static char *regatom(regex_t *preg, int *flagp );
+static char *regnode(regex_t *preg, int op );
+static const char *regnext(regex_t *preg, const char *p );
+static void regc(regex_t *preg, int b );
+static void reginsert(regex_t *preg, char op, char *opnd );
+static void regtail(regex_t *preg, char *p, const char *val );
+static void regoptail(regex_t *preg, char *p, const char *val );
+
+static const char *str_find(const char *string, char c, int nocase);
+
+/*#define DEBUG*/
+#ifdef DEBUG
+int regnarrate = 0;
+static void regdump(regex_t *preg);
+static const char *regprop( const char *op );
+#endif
+
+
+static char regdummy;
+
+/*
+ - regcomp - compile a regular expression into internal code
+ *
+ * We can't allocate space until we know how big the compiled form will be,
+ * but we can't compile it (and thus know how big it is) until we've got a
+ * place to put the code.  So we cheat:  we compile it twice, once with code
+ * generation turned off and size counting turned on, and once "for real".
+ * This also means that we don't allocate space until we are sure that the
+ * thing really will compile successfully, and we never have to move the
+ * code and thus invalidate pointers into it.  (Note that it has to be in
+ * one piece because free() must be able to free it all.)
+ *
+ * Beware that the optimization-preparation code in here knows about some
+ * of the structure of the compiled regexp.
+ */
+int regcomp(regex_t *preg, const char *exp, int cflags)
+{
+	const char *scan;
+	const char *longest;
+	unsigned len;
+	int flags;
+
+	memset(preg, 0, sizeof(*preg));
+
+	if (exp == NULL)
+		FAIL(preg, REG_ERR_NULL_ARGUMENT);
+
+	/* First pass: determine size, legality. */
+#ifdef notdef
+	if (exp[0] == '.' && exp[1] == '*') exp += 2;  /* aid grep */
+#endif
+	preg->cflags = cflags;
+	preg->regparse = (char *)exp;
+	preg->re_nsub = 1;
+	preg->regsize = 0L;
+	preg->regcode = &regdummy;
+	regc(preg, REG_MAGIC);
+	if (reg(preg, 0, &flags) == NULL)
+		return preg->err;
+
+	/* Small enough for pointer-storage convention? */
+	if (preg->regsize >= 32767L || preg->re_nsub >= REG_MAX_PAREN)		/* Probably could be 65535L. */
+		FAIL(preg,REG_ERR_TOO_BIG);
+
+	/* Allocate space. */
+	preg->program = malloc(preg->regsize);
+	if (preg->program == NULL)
+		FAIL(preg, REG_ERR_NOMEM);
+
+	/* Second pass: emit code. */
+	preg->regparse = (char *)exp;
+	preg->re_nsub = 1;
+	preg->regcode = preg->program;
+	regc(preg, REG_MAGIC);
+	if (reg(preg, 0, &flags) == NULL)
+		return preg->err;
+
+	/* Dig out information for optimizations. */
+	preg->regstart = '\0';	/* Worst-case defaults. */
+	preg->reganch = 0;
+	preg->regmust = NULL;
+	preg->regmlen = 0;
+	scan = preg->program+1;			/* First BRANCH. */
+	if (OP(regnext(preg, scan)) == END) {		/* Only one top-level choice. */
+		scan = OPERAND(scan);
+
+		/* Starting-point info. */
+		if (OP(scan) == EXACTLY)
+			preg->regstart = *OPERAND(scan);
+		else if (OP(scan) == BOL)
+			preg->reganch++;
+
+		/*
+		 * If there's something expensive in the r.e., find the
+		 * longest literal string that must appear and make it the
+		 * regmust.  Resolve ties in favor of later strings, since
+		 * the regstart check works with the beginning of the r.e.
+		 * and avoiding duplication strengthens checking.  Not a
+		 * strong reason, but sufficient in the absence of others.
+		 */
+		if (flags&SPSTART) {
+			longest = NULL;
+			len = 0;
+			for (; scan != NULL; scan = regnext(preg, scan))
+				if (OP(scan) == EXACTLY && strlen(OPERAND(scan)) >= len) {
+					longest = OPERAND(scan);
+					len = strlen(OPERAND(scan));
+				}
+			preg->regmust = longest;
+			preg->regmlen = len;
+		}
+	}
+
+#ifdef DEBUG
+	/*regdump(preg);*/
+#endif
+
+	return 0;
+}
+
+/*
+ - reg - regular expression, i.e. main body or parenthesized thing
+ *
+ * Caller must absorb opening parenthesis.
+ *
+ * Combining parenthesis handling with the base level of regular expression
+ * is a trifle forced, but the need to tie the tails of the branches to what
+ * follows makes it hard to avoid.
+ */
+static char *reg(regex_t *preg, int paren /* Parenthesized? */, int *flagp )
+{
+	char *ret;
+	char *br;
+	const char *ender;
+	int parno = 0;
+	int flags;
+
+	*flagp = HASWIDTH;	/* Tentatively. */
+
+	/* Make an OPEN node, if parenthesized. */
+	if (paren) {
+		parno = preg->re_nsub++;
+		ret = regnode(preg, OPEN+parno);
+	} else
+		ret = NULL;
+
+	/* Pick up the branches, linking them together. */
+	br = regbranch(preg, &flags);
+	if (br == NULL)
+		return(NULL);
+	if (ret != NULL)
+		regtail(preg, ret, br);	/* OPEN -> first. */
+	else
+		ret = br;
+	if (!(flags&HASWIDTH))
+		*flagp &= ~HASWIDTH;
+	*flagp |= flags&SPSTART;
+	while (*preg->regparse == '|' || *preg->regparse == '\n') {
+		preg->regparse++;
+		br = regbranch(preg, &flags);
+		if (br == NULL)
+			return(NULL);
+		regtail(preg, ret, br);	/* BRANCH -> BRANCH. */
+		if (!(flags&HASWIDTH))
+			*flagp &= ~HASWIDTH;
+		*flagp |= flags&SPSTART;
+	}
+
+	/* Make a closing node, and hook it on the end. */
+	ender = regnode(preg, (paren) ? CLOSE+parno : END);	
+	regtail(preg, ret, ender);
+
+	/* Hook the tails of the branches to the closing node. */
+	for (br = ret; br != NULL; br = (char *)regnext(preg, br))
+		regoptail(preg, br, ender);
+
+	/* Check for proper termination. */
+	if (paren && *preg->regparse++ != ')') {
+		preg->err = REG_ERR_UNMATCHED_PAREN;
+		return NULL;
+	} else if (!paren && *preg->regparse != '\0') {
+		if (*preg->regparse == ')') {
+			preg->err = REG_ERR_UNMATCHED_PAREN;
+			return NULL;
+		} else {
+			preg->err = REG_ERR_JUNK_ON_END;
+			return NULL;
+		}
+	}
+
+	return(ret);
+}
+
+/*
+ - regbranch - one alternative of an | operator
+ *
+ * Implements the concatenation operator.
+ */
+static char *regbranch(regex_t *preg, int *flagp )
+{
+	char *ret;
+	char *chain;
+	char *latest;
+	int flags;
+
+	*flagp = WORST;		/* Tentatively. */
+
+	ret = regnode(preg, BRANCH);
+	chain = NULL;
+	while (*preg->regparse != '\0' && *preg->regparse != ')' &&
+	       *preg->regparse != '\n' && *preg->regparse != '|') {
+		latest = regpiece(preg, &flags);
+		if (latest == NULL)
+			return(NULL);
+		*flagp |= flags&HASWIDTH;
+		if (chain == NULL)	/* First piece. */
+			*flagp |= flags&SPSTART;
+		else
+			regtail(preg, chain, latest);
+		chain = latest;
+	}
+	if (chain == NULL)	/* Loop ran zero times. */
+		(void) regnode(preg, NOTHING);
+
+	return(ret);
+}
+
+/*
+ - regpiece - something followed by possible [*+?]
+ *
+ * Note that the branching code sequences used for ? and the general cases
+ * of * and + are somewhat optimized:  they use the same NOTHING node as
+ * both the endmarker for their branch list and the body of the last branch.
+ * It might seem that this node could be dispensed with entirely, but the
+ * endmarker role is not redundant.
+ */
+static char *regpiece(regex_t *preg, int *flagp )
+{
+	char *ret;
+	char op;
+	char *next;
+	int flags;
+
+	ret = regatom(preg, &flags);
+	if (ret == NULL)
+		return(NULL);
+
+	op = *preg->regparse;
+	if (!ISMULT(op)) {
+		*flagp = flags;
+		return(ret);
+	}
+
+	if (!(flags&HASWIDTH) && op != '?') {
+		preg->err = REG_ERR_OPERAND_COULD_BE_EMPTY;
+		return NULL;
+	}
+	*flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);
+
+	if (op == '*' && (flags&SIMPLE))
+		reginsert(preg, STAR, ret);
+	else if (op == '*') {
+		/* Emit x* as (x&|), where & means "self". */
+		reginsert(preg, BRANCH, ret);			/* Either x */
+		regoptail(preg, ret, regnode(preg, BACK));		/* and loop */
+		regoptail(preg, ret, ret);			/* back */
+		regtail(preg, ret, regnode(preg, BRANCH));		/* or */
+		regtail(preg, ret, regnode(preg, NOTHING));		/* null. */
+	} else if (op == '+' && (flags&SIMPLE))
+		reginsert(preg, PLUS, ret);
+	else if (op == '+') {
+		/* Emit x+ as x(&|), where & means "self". */
+		next = regnode(preg, BRANCH);			/* Either */
+		regtail(preg, ret, next);
+		regtail(preg, regnode(preg, BACK), ret);		/* loop back */
+		regtail(preg, next, regnode(preg, BRANCH));		/* or */
+		regtail(preg, ret, regnode(preg, NOTHING));		/* null. */
+	} else if (op == '?') {
+		/* Emit x? as (x|) */
+		reginsert(preg, BRANCH, ret);			/* Either x */
+		regtail(preg, ret, regnode(preg, BRANCH));		/* or */
+		next = regnode(preg, NOTHING);		/* null. */
+		regtail(preg, ret, next);
+		regoptail(preg, ret, next);
+	}
+	preg->regparse++;
+	if (ISMULT(*preg->regparse)) {
+		preg->err = REG_ERR_NESTED_COUNT;
+		return NULL;
+	}
+
+	return(ret);
+}
+
+static void reg_addrange(regex_t *preg, int lower, int upper)
+{
+	if (lower > upper) {
+		reg_addrange(preg, upper, lower);
+	}
+	while (lower <= upper) {
+		regc(preg, lower++);
+	}
+}
+
+static void reg_addstr(regex_t *preg, const char *str)
+{
+	while (*str) {
+		regc(preg, *str++);
+	}
+}
+
+/*
+ - regatom - the lowest level
+ *
+ * Optimization:  gobbles an entire sequence of ordinary characters so that
+ * it can turn them into a single node, which is smaller to store and
+ * faster to run.  Backslashed characters are exceptions, each becoming a
+ * separate node; the code is simpler that way and it's not worth fixing.
+ */
+static char *regatom(regex_t *preg, int *flagp )
+{
+	char *ret;
+	int flags;
+
+	*flagp = WORST;		/* Tentatively. */
+
+	switch (*preg->regparse++) {
+	/* FIXME: these chars only have meaning at beg/end of pat? */
+	case '^':
+		ret = regnode(preg, BOL);
+		break;
+	case '$':
+		ret = regnode(preg, EOL);
+		break;
+	case '.':
+		ret = regnode(preg, ANY);
+		*flagp |= HASWIDTH|SIMPLE;
+		break;
+	case '[': {
+			if (*preg->regparse == '^') {	/* Complement of range. */
+				ret = regnode(preg, ANYBUT);
+				preg->regparse++;
+			} else
+				ret = regnode(preg, ANYOF);
+			if (*preg->regparse == ']' || *preg->regparse == '-')
+				regc(preg, *preg->regparse++);
+			while (*preg->regparse != '\0' && *preg->regparse != ']') {
+				if (*preg->regparse == '-') {
+					preg->regparse++;
+					if (*preg->regparse == ']' || *preg->regparse == '\0')
+						regc(preg, '-');
+					else {
+						reg_addrange(preg, UCHARAT(preg->regparse-2), UCHARAT(preg->regparse));
+						preg->regparse++;
+					}
+				} else if (strncmp(preg->regparse, "[:alpha:]", 9) == 0) {
+					reg_addrange(preg,'a','z');
+					reg_addrange(preg,'A','Z');
+					preg->regparse += 9;
+				} else if (strncmp(preg->regparse, "[:alnum:]", 9) == 0) {
+					reg_addrange(preg,'a','z');
+					reg_addrange(preg,'A','Z');
+					reg_addrange(preg,'0','9');
+					preg->regparse += 9;
+				} else if (strncmp(preg->regparse, "[:space:]", 9) == 0) {
+					reg_addstr(preg," \t\r\n\f\v");
+					preg->regparse += 9;
+				} else
+					regc(preg, *preg->regparse++);
+			}
+			regc(preg, '\0');
+			if (*preg->regparse == ']') {
+				preg->regparse++;
+			}
+			*flagp |= HASWIDTH|SIMPLE;
+		}
+		break;
+	case '(':
+		ret = reg(preg, 1, &flags);
+		if (ret == NULL)
+			return(NULL);
+		*flagp |= flags&(HASWIDTH|SPSTART);
+		break;
+	case '\0':
+	case '|':
+	case '\n':
+	case ')':
+		preg->err = REG_ERR_INTERNAL;
+		return NULL;	/* Supposed to be caught earlier. */
+	case '?':
+	case '+':
+	case '*':
+		preg->err = REG_ERR_COUNT_FOLLOWS_NOTHING;
+		return NULL;
+	case '{':
+		preg->err = REG_ERR_COUNT_UNSUPPORTED;
+		return NULL;
+	case '\\':
+		switch (*preg->regparse++) {
+		case '\0':
+			preg->err = REG_ERR_TRAILING_BACKSLASH;
+			return NULL;
+			break;
+		case '<':
+			ret = regnode(preg, WORDA);
+			break;
+		case '>':
+			ret = regnode(preg, WORDZ);
+			break;
+		case 'd':
+			ret = regnode(preg, ANYOF);
+			reg_addrange(preg, '0', '9');
+			regc(preg, '\0');
+			*flagp |= HASWIDTH|SIMPLE;
+			break;
+		case 'w':
+			ret = regnode(preg, ANYOF);
+			reg_addrange(preg, 'a', 'z');
+			reg_addrange(preg, 'A', 'Z');
+			reg_addrange(preg, '0', '9');
+			regc(preg, '_');
+			regc(preg, '\0');
+			*flagp |= HASWIDTH|SIMPLE;
+			break;
+		case 's':
+			ret = regnode(preg, ANYOF);
+			reg_addstr(preg," \t\r\n\f\v");
+			regc(preg, '\0');
+			*flagp |= HASWIDTH|SIMPLE;
+			break;
+		/* FIXME: Someday handle \1, \2, ... */
+		default:
+			/* Handle general quoted chars in exact-match routine */
+			goto de_fault;
+		}
+		break;
+	de_fault:
+	default:
+		/*
+		 * Encode a string of characters to be matched exactly.
+		 *
+		 * This is a bit tricky due to quoted chars and due to
+		 * '*', '+', and '?' taking the SINGLE char previous
+		 * as their operand.
+		 *
+		 * On entry, the char at regparse[-1] is going to go
+		 * into the string, no matter what it is.  (It could be
+		 * following a \ if we are entered from the '\' case.)
+		 * 
+		 * Basic idea is to pick up a good char in  ch  and
+		 * examine the next char.  If it's *+? then we twiddle.
+		 * If it's \ then we frozzle.  If it's other magic char
+		 * we push  ch  and terminate the string.  If none of the
+		 * above, we push  ch  on the string and go around again.
+		 *
+		 *  regprev  is used to remember where "the current char"
+		 * starts in the string, if due to a *+? we need to back
+		 * up and put the current char in a separate, 1-char, string.
+		 * When  regprev  is NULL,  ch  is the only char in the
+		 * string; this is used in *+? handling, and in setting
+		 * flags |= SIMPLE at the end.
+		 */
+		{
+			const char *regprev;
+			char ch;
+
+			preg->regparse--;			/* Look at cur char */
+			ret = regnode(preg, EXACTLY);
+			for ( regprev = 0 ; ; ) {
+				ch = *preg->regparse++;	/* Get current char */
+				switch (*preg->regparse) {	/* look at next one */
+
+				default:
+					regc(preg, ch);	/* Add cur to string */
+					break;
+
+				case '.': case '[': case '(':
+				case ')': case '|': case '\n':
+				case '$': case '^':
+				case '\0':
+				/* FIXME, $ and ^ should not always be magic */
+				magic:
+					regc(preg, ch);	/* dump cur char */
+					goto done;	/* and we are done */
+
+				case '?': case '+': case '*':
+					if (!regprev) 	/* If just ch in str, */
+						goto magic;	/* use it */
+					/* End mult-char string one early */
+					preg->regparse = regprev; /* Back up parse */
+					goto done;
+
+				case '\\':
+					regc(preg, ch);	/* Cur char OK */
+					switch (preg->regparse[1]){ /* Look after \ */
+					case '\0':
+					case '<':
+					case '>':
+					/* FIXME: Someday handle \1, \2, ... */
+						goto done; /* Not quoted */
+					default:
+						/* Backup point is \, scan							 * point is after it. */
+						regprev = preg->regparse;
+						preg->regparse++; 
+						continue;	/* NOT break; */
+					}
+				}
+				regprev = preg->regparse;	/* Set backup point */
+			}
+		done:
+			regc(preg, '\0');
+			*flagp |= HASWIDTH;
+			if (!regprev)		/* One char? */
+				*flagp |= SIMPLE;
+		}
+		break;
+	}
+
+	return(ret);
+}
+
+/*
+ - regnode - emit a node
+ */
+/* Location. */
+static char *regnode(regex_t *preg, int op)
+{
+	char *ret;
+	char *ptr;
+
+	ret = preg->regcode;
+	if (ret == &regdummy) {
+		preg->regsize += 3;
+		return(ret);
+	}
+
+	ptr = ret;
+	*ptr++ = op;
+	*ptr++ = '\0';		/* Null "next" pointer. */
+	*ptr++ = '\0';
+	preg->regcode = ptr;
+
+	return(ret);
+}
+
+/*
+ - regc - emit (if appropriate) a byte of code
+ */
+static void regc(regex_t *preg, int b )
+{
+	if (preg->regcode != &regdummy)
+		*preg->regcode++ = b;
+	else
+		preg->regsize++;
+}
+
+/*
+ - reginsert - insert an operator in front of already-emitted operand
+ *
+ * Means relocating the operand.
+ */
+static void reginsert(regex_t *preg, char op, char *opnd )
+{
+	char *src;
+	char *dst;
+	char *place;
+
+	if (preg->regcode == &regdummy) {
+		preg->regsize += 3;
+		return;
+	}
+
+	src = preg->regcode;
+	preg->regcode += 3;
+	dst = preg->regcode;
+	while (src > opnd)
+		*--dst = *--src;
+
+	place = opnd;		/* Op node, where operand used to be. */
+	*place++ = op;
+	*place++ = '\0';
+	*place = '\0';
+}
+
+/*
+ - regtail - set the next-pointer at the end of a node chain
+ */
+static void regtail(regex_t *preg, char *p, const char *val )
+{
+	char *scan;
+	char *temp;
+	int offset;
+
+	if (p == &regdummy)
+		return;
+
+	/* Find last node. */
+	scan = p;
+	for (;;) {
+		temp = (char *)regnext(preg, scan);
+		if (temp == NULL)
+			break;
+		scan = temp;
+	}
+
+	if (OP(scan) == BACK)
+		offset = scan - val;
+	else
+		offset = val - scan;
+	*(scan+1) = (offset>>8)&0377;
+	*(scan+2) = offset&0377;
+}
+
+/*
+ - regoptail - regtail on operand of first argument; nop if operandless
+ */
+
+static void regoptail(regex_t *preg, char *p, const char *val )
+{
+	/* "Operandless" and "op != BRANCH" are synonymous in practice. */
+	if (p == NULL || p == &regdummy || OP(p) != BRANCH)
+		return;
+	regtail(preg, OPERAND(p), val);
+}
+
+/*
+ * regexec and friends
+ */
+
+/*
+ * Forwards.
+ */
+static int regtry(regex_t *preg, const char *string );
+static int regmatch(regex_t *preg, const char *prog);
+static int regrepeat(regex_t *preg, const char *p );
+
+/*
+ - regexec - match a regexp against a string
+ */
+int regexec(regex_t  *preg,  const  char *string, size_t nmatch, regmatch_t pmatch[], int eflags)
+{
+	const char *s;
+
+	/* Be paranoid... */
+	if (preg == NULL || preg->program == NULL || string == NULL) {
+		return REG_ERR_NULL_ARGUMENT;
+	}
+
+	/* Check validity of program. */
+	if (UCHARAT(preg->program) != REG_MAGIC) {
+		return REG_ERR_CORRUPTED;
+	}
+
+#ifdef DEBUG
+	/*regdump(preg);*/
+#endif
+
+	preg->eflags = eflags;
+	preg->pmatch = pmatch;
+	preg->nmatch = nmatch;
+	preg->start = string;	/* All offsets are computed from here */
+
+	/* If there is a "must appear" string, look for it. */
+	if (preg->regmust != NULL) {
+		s = string;
+		while ((s = str_find(s, preg->regmust[0], preg->cflags & REG_ICASE)) != NULL) {
+			if (strncmp(s, preg->regmust, preg->regmlen) == 0)
+				break;	/* Found it. */
+			s++;
+		}
+		if (s == NULL)	/* Not present. */
+			return REG_NOMATCH;
+	}
+
+	/* Mark beginning of line for ^ . */
+	preg->regbol = string;
+
+	/* Simplest case:  anchored match need be tried only once (maybe per line). */
+	if (preg->reganch) {
+		if (eflags & REG_NOTBOL) {
+			/* This is an anchored search, but not an BOL, so possibly skip to the next line */
+			goto nextline;
+		}
+		while (1) {
+			int ret = regtry(preg, string);
+			if (ret) {
+				return REG_NOERROR;
+			}
+			if (*preg->reginput) {
+nextline:
+				if (preg->cflags & REG_NEWLINE) {
+					/* Try the next anchor? */
+					string = strchr(preg->reginput, '\n');
+					if (string) {
+						preg->regbol = ++string;
+						continue;
+					}
+				}
+			}
+			return REG_NOMATCH;
+		}
+	}
+
+	/* Messy cases:  unanchored match. */
+	s = string;
+	if (preg->regstart != '\0') {
+		/* We know what char it must start with. */
+		while ((s = str_find(s, preg->regstart, preg->cflags & REG_ICASE)) != NULL) {
+			if (regtry(preg, s))
+				return REG_NOERROR;
+			s++;
+		}
+	}
+	else
+		/* We don't -- general case. */
+		do {
+			if (regtry(preg, s))
+				return REG_NOERROR;
+		} while (*s++ != '\0');
+
+	/* Failure. */
+	return REG_NOMATCH;
+}
+
+/*
+ - regtry - try match at specific point
+ */
+			/* 0 failure, 1 success */
+static int regtry( regex_t *preg, const char *string )
+{
+	int i;
+
+	preg->reginput = string;
+
+	for (i = 0; i < preg->nmatch; i++) {
+		preg->pmatch[i].rm_so = -1;
+		preg->pmatch[i].rm_eo = -1;
+	}
+	if (regmatch(preg, preg->program + 1)) {
+		preg->pmatch[0].rm_so = string - preg->start;
+		preg->pmatch[0].rm_eo = preg->reginput - preg->start;
+		return(1);
+	} else
+		return(0);
+}
+
+/**
+ * Returns 1 if 'pattern' is a prefix of 'string'.
+ *
+ * If 'nocase' is non-zero, does a case-insensitive match.
+ */
+static int prefix_cmp(const char *pattern, const char *string, int nocase)
+{
+	if (nocase) {
+		while (*pattern && *string) {
+			if (toupper(*pattern) != toupper(*string)) {
+				break;
+			}
+			pattern++;
+			string++;
+		}
+		return *pattern == 0;
+	}
+	else {
+		if (*pattern == *string) {
+			int len = strlen(pattern);
+			return strncmp(pattern, string, len) == 0;
+		}
+		return 0;
+	}
+}
+
+static const char *str_find(const char *string, char c, int nocase)
+{
+	if (nocase) {
+		c = toupper(c);
+		while (*string) {
+			if (toupper(*string) == c) {
+				return string;
+			}
+			string++;
+		}
+		return NULL;
+	}
+	else {
+		return strchr(string, c);
+	}
+}
+
+static int reg_iseol(regex_t *preg, int ch)
+{
+	if (preg->cflags & REG_NEWLINE) {
+		return ch == '\0' || ch == '\n';
+	}
+	else {
+		return ch == '\0';
+	}
+}
+
+/*
+ - regmatch - main matching routine
+ *
+ * Conceptually the strategy is simple:  check to see whether the current
+ * node matches, call self recursively to see whether the rest matches,
+ * and then act accordingly.  In practice we make some effort to avoid
+ * recursion, in particular by going through "ordinary" nodes (that don't
+ * need to know whether the rest of the match failed) by a loop instead of
+ * by recursion.
+ */
+/* 0 failure, 1 success */
+static int regmatch(regex_t *preg, const char *prog)
+{
+	const char *scan;	/* Current node. */
+	const char *next;		/* Next node. */
+
+	scan = prog;
+#ifdef DEBUG
+	if (scan != NULL && regnarrate)
+		fprintf(stderr, "%s(\n", regprop(scan));
+#endif
+	while (scan != NULL) {
+#ifdef DEBUG
+		if (regnarrate)
+			fprintf(stderr, "%s...\n", regprop(scan));
+#endif
+		next = regnext(preg, scan);
+
+		switch (OP(scan)) {
+		case BOL:
+			if (preg->reginput != preg->regbol)
+				return(0);
+			break;
+		case EOL:
+			if (!reg_iseol(preg, *preg->reginput)) {
+				return(0);
+			}
+			break;
+		case WORDA:
+			/* Must be looking at a letter, digit, or _ */
+			if ((!isalnum(*preg->reginput)) && *preg->reginput != '_')
+				return(0);
+			/* Prev must be BOL or nonword */
+			if (preg->reginput > preg->regbol &&
+			    (isalnum(preg->reginput[-1]) || preg->reginput[-1] == '_'))
+				return(0);
+			break;
+		case WORDZ:
+			/* Must be looking at non letter, digit, or _ */
+			if (isalnum(*preg->reginput) || *preg->reginput == '_')
+				return(0);
+			/* We don't care what the previous char was */
+			break;
+		case ANY:
+			if (reg_iseol(preg, *preg->reginput))
+				return 0;
+			preg->reginput++;
+			break;
+		case EXACTLY: {
+				const char *opnd;
+
+				opnd = OPERAND(scan);
+
+				if (prefix_cmp(opnd, preg->reginput, preg->cflags & REG_ICASE) == 0) {
+					return(0);
+				}
+				preg->reginput += strlen(opnd);
+			}
+			break;
+		case ANYOF:
+			if (reg_iseol(preg, *preg->reginput))
+				return 0;
+ 			if (str_find(OPERAND(scan), *preg->reginput, preg->cflags & REG_ICASE) == NULL)
+				return(0);
+			preg->reginput++;
+			break;
+		case ANYBUT:
+			if (reg_iseol(preg, *preg->reginput))
+				return 0;
+ 			if (str_find(OPERAND(scan), *preg->reginput, preg->cflags & REG_ICASE) != NULL)
+				return(0);
+			preg->reginput++;
+			break;
+		case NOTHING:
+			break;
+		case BACK:
+			break;
+		case BRANCH: {
+				const char *save;
+
+				if (OP(next) != BRANCH)		/* No choice. */
+					next = OPERAND(scan);	/* Avoid recursion. */
+				else {
+					do {
+						save = preg->reginput;
+						if (regmatch(preg, OPERAND(scan)))
+							return(1);
+						preg->reginput = save;
+						scan = regnext(preg, scan);
+					} while (scan != NULL && OP(scan) == BRANCH);
+					return(0);
+					/* NOTREACHED */
+				}
+			}
+			break;
+		case STAR:
+		case PLUS: {
+				char nextch;
+				int no;
+				const char *save;
+				int min;
+
+				/*
+				 * Lookahead to avoid useless match attempts
+				 * when we know what character comes next.
+				 */
+				nextch = '\0';
+				if (OP(next) == EXACTLY)
+					nextch = *OPERAND(next);
+				min = (OP(scan) == STAR) ? 0 : 1;
+				save = preg->reginput;
+				no = regrepeat(preg, OPERAND(scan));
+				while (no >= min) {
+					/* If it could work, try it. */
+					if (reg_iseol(preg, nextch) || *preg->reginput == nextch)
+						if (regmatch(preg, next))
+							return(1);
+					/* Couldn't or didn't -- back up. */
+					no--;
+					preg->reginput = save + no;
+				}
+				return(0);
+			}
+			break;
+		case END:
+			return(1);	/* Success! */
+			break;
+		default:
+			if (OP(scan) >= OPEN+1 && OP(scan) < CLOSE_END) {
+				const char *save;
+
+				save = preg->reginput;
+
+				if (regmatch(preg, next)) {
+					int no;
+					/*
+					 * Don't set startp if some later
+					 * invocation of the same parentheses
+					 * already has.
+					 */
+					if (OP(scan) < CLOSE) {
+						no = OP(scan) - OPEN;
+						if (no < preg->nmatch && preg->pmatch[no].rm_so == -1) {
+							preg->pmatch[no].rm_so = save - preg->start;
+						}
+					}
+					else {
+						no = OP(scan) - CLOSE;
+						if (no < preg->nmatch && preg->pmatch[no].rm_eo == -1) {
+							preg->pmatch[no].rm_eo = save - preg->start;
+						}
+					}
+					return(1);
+				} else
+					return(0);
+			}
+			return REG_ERR_INTERNAL;
+		}
+
+		scan = next;
+	}
+
+	/*
+	 * We get here only if there's trouble -- normally "case END" is
+	 * the terminating point.
+	 */
+	return REG_ERR_INTERNAL;
+}
+
+/*
+ - regrepeat - repeatedly match something simple, report how many
+ */
+static int regrepeat(regex_t *preg, const char *p )
+{
+	int count = 0;
+	const char *scan;
+	const char *opnd;
+
+	scan = preg->reginput;
+	opnd = OPERAND(p);
+	switch (OP(p)) {
+	case ANY:
+		while (!reg_iseol(preg, *scan)) {
+			count++;
+			scan++;
+		}
+		break;
+	case EXACTLY:
+		if (preg->cflags & REG_ICASE) {
+			while (toupper(*opnd) == toupper(*scan)) {
+				count++;
+				scan++;
+			}
+		}
+		else {
+			while (*opnd == *scan) {
+				count++;
+				scan++;
+			}
+		}
+		break;
+	case ANYOF:
+		while (!reg_iseol(preg, *scan) && str_find(opnd, *scan, preg->cflags & REG_ICASE) != NULL) {
+			count++;
+			scan++;
+		}
+		break;
+	case ANYBUT:
+		while (!reg_iseol(preg, *scan) && str_find(opnd, *scan, preg->cflags & REG_ICASE) == NULL) {
+			count++;
+			scan++;
+		}
+		break;
+	default:		/* Oh dear.  Called inappropriately. */
+		preg->err = REG_ERR_INTERNAL;
+		count = 0;	/* Best compromise. */
+		break;
+	}
+	preg->reginput = scan;
+
+	return(count);
+}
+
+/*
+ - regnext - dig the "next" pointer out of a node
+ */
+static const char *regnext(regex_t *preg, const char *p )
+{
+	int offset;
+
+	if (p == &regdummy)
+		return(NULL);
+
+	offset = NEXT(p);
+	if (offset == 0)
+		return(NULL);
+
+	if (OP(p) == BACK)
+		return(p-offset);
+	else
+		return(p+offset);
+}
+
+#ifdef DEBUG
+
+/*
+ - regdump - dump a regexp onto stdout in vaguely comprehensible form
+ */
+static void regdump(regex_t *preg)
+{
+	const char *s;
+	char op = EXACTLY;	/* Arbitrary non-END op. */
+	const char *next;
+
+
+	s = preg->program + 1;
+	while (op != END) {	/* While that wasn't END last time... */
+		op = OP(s);
+		printf("%2d%s", (int)(s-preg->program), regprop(s));	/* Where, what. */
+		next = regnext(preg, s);
+		if (next == NULL)		/* Next ptr. */
+			printf("(0)");
+		else 
+			printf("(%d)", (int)((s-preg->program)+(next-s)));
+		s += 3;
+		if (op == ANYOF || op == ANYBUT || op == EXACTLY) {
+			/* Literal string, where present. */
+			while (*s != '\0') {
+				putchar(*s);
+				s++;
+			}
+			s++;
+		}
+		putchar('\n');
+	}
+
+	/* Header fields of interest. */
+	if (preg->regstart != '\0')
+		printf("start `%c' ", preg->regstart);
+	if (preg->reganch)
+		printf("anchored ");
+	if (preg->regmust != NULL)
+		printf("must have \"%s\"", preg->regmust);
+	printf("\n");
+}
+
+/*
+ - regprop - printable representation of opcode
+ */
+static const char *regprop( const char *op )
+{
+	char *p;
+	static char buf[50];
+
+	(void) strcpy(buf, ":");
+
+	switch (OP(op)) {
+	case BOL:
+		p = "BOL";
+		break;
+	case EOL:
+		p = "EOL";
+		break;
+	case ANY:
+		p = "ANY";
+		break;
+	case ANYOF:
+		p = "ANYOF";
+		break;
+	case ANYBUT:
+		p = "ANYBUT";
+		break;
+	case BRANCH:
+		p = "BRANCH";
+		break;
+	case EXACTLY:
+		p = "EXACTLY";
+		break;
+	case NOTHING:
+		p = "NOTHING";
+		break;
+	case BACK:
+		p = "BACK";
+		break;
+	case END:
+		p = "END";
+		break;
+	case STAR:
+		p = "STAR";
+		break;
+	case PLUS:
+		p = "PLUS";
+		break;
+	case WORDA:
+		p = "WORDA";
+		break;
+	case WORDZ:
+		p = "WORDZ";
+		break;
+	default:
+		if (OP(op) >= OPEN && OP(op) < CLOSE) {
+			sprintf(buf+strlen(buf), "OPEN%d", OP(op)-OPEN);
+		}
+		else if (OP(op) >= CLOSE && OP(op) < CLOSE_END) {
+			sprintf(buf+strlen(buf), "CLOSE%d", OP(op)-CLOSE);
+		}
+		else {
+			abort();
+		}
+		p = NULL;
+		break;
+	}
+	if (p != NULL)
+		(void) strcat(buf, p);
+	return(buf);
+}
+#endif
+
+size_t regerror(int errcode, const regex_t *preg, char *errbuf,  size_t errbuf_size)
+{
+	static const char *error_strings[] = {
+		"success",
+		"no match",
+		"bad pattern",
+		"null argument",
+		"unknown error",
+		"too big",
+		"out of memory",
+		"too many ()",
+		"parentheses () not balanced",
+		"extra characters",
+		"*+ of empty atom",
+		"nested count",
+		"internal error",
+		"count follows nothing",
+		"trailing backslash",
+		"corrupted program",
+		"braces {} not supported"
+	};
+	const char *err;
+
+	if (errcode < 0 || errcode >= REG_ERR_NUM) {
+		err = "Bad error code";
+	}
+	else {
+		err = error_strings[errcode];
+	}
+
+	return snprintf(errbuf, errbuf_size, "%s", err);
+}
+
+void regfree(regex_t *preg)
+{
+	free(preg->program);
+}
+
+#endif